Suppose that there are four green and six red marbles in a box, and two are taken out, with no replacement. Let X; and X, be indicator random variables connected with selecting a green marble, so that X; = 1 if the ith selected marble is green and zero otherwise. (a) Determine the joint PDF of Xi and X2. (b) Determine the marginal PDFs of Xi and X2. (c) Are X1 and X, independent? (d) Determine the conditional PDFs of X1 given X2 = 1 and of X2 given Xi = 0.

Determine the probability P(X1 +X2 =1)